a. Field of the Invention
This invention relates to improvements in injection molding.
B. Description of Prior Art
Injection molding apparatus presently used has several disadvantages. The ejection of the molded parts from the apparatus can be difficult or awkward when the parting line between the molds defining the mold cavities in which the parts are molded, is horizontal. Usually individual knock-out pins are required, one or more for each molded part, to remove it from the molding apparatus, and this can make the apparatus expensive.
Ejection of the molded parts can also be difficult if the parts to be molded have an uneven base. The knock-out pin or pins may not apply uniform force on the part when stripping it from a core if it acts or they act against an uneven base and damage to the part can occur.
A further disadvantage in injection molding is that the waste or sprue member, which comprises molding material that has set in the channels and passages leading to the mold cavities after molding must be manually separated from the parts molded in the cavities. This is time consuming and expensive. Also, the separation operation may leave a rough surface area on the finished part which may necessitate a further operation to clean or smooth the rough surface area.
A further disadvantage is the face that known injection molding apparatus employs integral molds which have both the mold defining surface and the positioning and moving means on the same member; because of this use of integral molds, it is very difficult and time consuming to change an injection molding machine to mold different parts. Also, the molds required for different parts are expensive since each mold must include both and the mold defining surface and the positioning and moving means.